1. Field of the Invention
The present invention relates to a hydrogen purification module, and more particularly to a hydrogen purification module, which is comprised of unit cells, each having metal membranes permeable by hydrogen, by coupling individual fittings of the unit cells.
2. Description of the Prior Art
A hydrogen purification module is a device for purifying mixed gas containing hydrogen, or low-purity reformed hydrogen, into high-purity hydrogen. The hydrogen purification module functions to produce high-purity hydrogen by selectively extracting only pure hydrogen from reformed gas produced by reforming hydrocarbon fuel such as gasoline, ethanol, methanol and natural gas, low-purity general hydrogen, or mixed gases containing hydrogen.
The hydrogen purification module can be used in producing high-purity hydrogen from low-purity regular hydrogen, and can be used as a hydrogen purification module for a small fuel reformer, which serves to remove impurities such as CO, by being connected to a reformer for reforming hydrocarbon fuel such as gasoline, ethanol, methanol or natural gas. The hydrogen purification module can also be applied to a small sized fuel reforming apparatus of a small sized system for generating electrical energy in combination with a fuel cell system, and can be applied to a small fuel reformer of a fuel cell powered vehicle.
U.S. Pat. No. 5,498,278 discloses a hydrogen separation membrane and a hydrogen separation module having a hydrogen separation membrane. The hydrogen separation membrane is comprised of a hydrogen-permeable metal coating layer, a support matrix and a porous layer disposed between the metal coating layer and the support matrix. With the hydrogen separation membrane, a plate-and-frame type hydrogen purification module or a shell-and-tube type hydrogen purification module is produced. Purification of hydrogen in this type of hydrogen purification module is achieved at high temperatures of 200° C.-1000° C. However, this type of hydrogen purification module has not only heat loss but also a chance of leakage of purified hydrogen due to components such as gaskets. Furthermore, this type of hydrogen purification module has a complicated structure and a heavy weight.
U.S. Pat. No. 5,645,626 discloses a cylindrical hydrogen purification module. The hydrogen purification module includes an inlet, an hydrogen outlet, a raffinate outlet and a hydrogen-permeable membrane. In this type of hydrogen purification module, a coating metal layer, a support matrix and an intermediate layer of a flat plate are commonly formed with central vertical holes. There is the provision of a gas-tight seal around the periphery of the holes through a metal coating layer of the membrane to prevent the leakage of hydrogen. Hydrogen, permeated through the metal membrane, passes through the hole of the hydrogen-permeable metal membrane. The hydrogen-permeable membrane is provided with a peripheral hollow, which may be a notch, a slot, a series of notches or slots, or a truncated section at the perimeter thereof. Such a hydrogen purification module also has disadvantages in that its operational temperature is limited, it is not suitable to generate ultrapure hydrogen due to heat loss at flange, and its weight is increased due to the gasket.
U.S. Pat. No. 5,997,594 discloses a steam reformer within internal hydrogen purification, which includes a reforming chamber having a reformation catalyst for producing reformed gas containing hydrogen from feed gas, and a metal membrane for dividing the reformed gas into byproduct gas and hydrogen gas. The steam reformer is provided with a tube-shaped hydrogen-permeable membrane.
As described above, the above-mentioned conventional hydrogen purification modules have disadvantages in that it is difficult to achieve a compact structure due to their complicated structures, and to achieve high-purity hydrogen, due to leakage of purified hydrogen. Furthermore, conventional hydrogen purification modules have a disadvantage in that components such as gaskets are damaged at the temperatures required to purify hydrogen, resulting in heat loss.
In addition, though the conventional hydrogen purification modules must be simply and compactly constructed in order to be used in a small fuel reformer for fuel cell powered vehicles, conventional hydrogen purification modules cannot be compactly constructed because of complicated structures and assemblies.